Above ground, infrasound activity is measured. Infrasound is defined as sound at frequencies below 20 Hz. However, in order to determine the infrasound levels, wind noise typically needs to be filtered out. Instruments which filter out the wind noise typically use a microphone that is connected to a long “soaker hose.” The infrasound levels are determined after averaging out the wind noise with the soaker hose. However, the soaker hose is deemed ineffective with wind speeds above 2.5 meters per second.